Lubricating oil composition



Patented A pr. 3,

'3 UNITED STATES. PATENT OFFICE,- z,:1 z,965

Cslif..' a corporation of Delaware No Drawing. Application March 15, 1944,

x Serial No. 526.841

- 8Claims. imam-'53) This invention relates to compounded mineral lubricating oils and more particularly'deals with lubricating oils containing oil-soluble metalloorganic detergent which possess the property of softening carbon, preventing orretardlng sticking of piston rings and deposition of lacquer in inter.-

nal combustion engines when running these enengines due to incomplete combustion. piston rings have a tendency to become stuck in the grooves. Lacquer and/or carbon formation appear to be the rence.

Moreover, so of top lands due to the formation of hard carbon, particularly when using high viscosity-index oils, may cause serious damage'to the engine.

To eliminate or reduce the lacquer deposition, ring-sticking, and hard carbon forming characteristics of oils it is necessary to compound them with additives, normally metal soaps, which seek zip-improve the oils in one or more of its proper- Polyvalent metal salts have been considered in the past as the best ofsuch metallic detergents as shown by their general acceptance by the'lubricating industry. Salts of the monovalent a1- kali metals, however, due to their notable insolubility in petroleum, have been little used, except whereresort has been had to colloidal dispersion by'mechanical means, or to the use-of auxiliary solvents or to other procedures for obutaining an adequate'concentration of such addi-.

ves.

It has now been found, however, that the alkali metal-that is, sodi m, potassium, and iithium salts of certain phthalic acid mono esters possess not only unexpected solubility in refined lubricating oil but lubricating oils com taining them are also characterized by extraordinary detergency and the ability to render the remaining small carbon deposits which form in engine operation extremely soft as contrasted withthe usual hard (and abundant) carbon deposit ordinarily found. The use of such a lubricant in an internal combustion engine rsmits in a most unique decrease or elimination of stuck piston rings, absence of the usual lacquer deposition, and associated principal reasons for this occur- The compounds of the mula in which M is sodium, potassium or lithium andv R represents an aliphatic highly branched hydrocarbon radical, containing from about 10 to 20 carbon atoms and preferably about 14 to- 20 carbon atoms, at least two of which carbon atoms.

and preferably more, are tertiary or quaternary carbon atoms. For reason of stability R should contain not more than one, and preferably nooleflnic double bonds. Suitable values of R are the alkyl radicals corresponding to the following illustrative list of branched paraflins foundin petroleum:

10 carbon atoms: dimethyloctane, trimethylheptane, methylethyiheptane, isopropylheptana tetrainethylhexane, diethylhexahe ll carbon atoms: dimetlwlnonane, trimethyloctane, tetramethylheptane, pentamethylhexane 12 carbon atoms: dimethyldecane, tetramethyloctane; methylpropyloctane, diethyloctane, dimethylpropylheptane, dimethylisopropylheptane, penta'metbylheptane I 18 carbon atoms: dimethylundecane, trimethyldecane 14 carbon atoms: dimethyldodecane, dipropyi- 20 carbon atoms: 'dimethyloctadecane, tetra- 18 carbon atoms: diethyltetradecane, 'dibutyldecane 19 carbon atoms: trimethylisobutyldodecane, trimethylhexadecane methylhexadecane. triethyltetradecsne.

However, suitable aikyi radicals are not limited I to those naturally occurring in petroleum. Such radicals may also contain halogens, for example chlorine, or other suitable substituents of high thermal stability. I I

Suitable amounts of the present metallo-orgsnwhich an anti-ring-sticking and soi't invention have the fordlpropylcarbon forming oil should contain range from about 0.25% up to the solubility limit or 10.0% whichever is the lower and preferably from about 0.75 to 5.0% but not exceeding the solubility limit.

The lubricating oils in which these additives may be used include petroleum or mineral oils as well as various hydrogenated, polymerized and otherwise synthetic and treated oils suchas voltolized oils, oils produced by polymerization of olefins and the like. Furthermore, the lubricat- .eral lubricating oil, while a corresponding phthalai'e containing a highly branched alkyl radical instead of the cetyl radical, was quite soluble in the same oil, as shown in the example below,

Example The sodium mono n-cetyl ester of phthalic acid was found to be soluble in a Mid-Continent lubricating oil "distillate less than 0.25%, and caused gel formation in the oil. On the other hand, the barium salt of this acid and the sodium heptadecyl phthalate, prepared from a branched alcohol of the formula CsHr-CH-(CzHi):

CSHr-C were observed to be readily soluble in more'than 6% in the some oil without causing gelling of theoil.

Samples of a refined commercial SAE 10 motor oil were compounded with 2% w. each of the barium n-cetyl phthalate and the above sodium heptadecyl phthalate respectively. The doped oils as well as a sample of the undoped oil were tested individually in a Fairbanks-Morse Diesel ensine operating at 1200 R. P. M. with a crank case temperature of 150:10 F. for 40 hours. The base oil alone gave a very unsatisfactory hard top land deposit. The oil containing the barium salt produced a smaller but fairly hard deposit of borderline acceptability. ,The oil conno-c various fatty acids of, say, 10 to 30 carbon atoms. wool fat acids, paraflin wax acids (produced by oxidation of parafiin wax), chlorinated fatty acids, aromatic carboxylic acids including aryl fatty acids, aryl hydroxy fatty acids, paraflln wax benzoic acids, various alkyl' salicyclic acids, phthalic acid mono esters, aromatic keto acids, aromatic ether acids; diphenols as di-(alkylphenol) sulfides and disulfldes, methylene bisalkylphenols; sulfonic acids such as may be pro duced by treatment of alkyl aromatic hydrocarbons or high boiling petroleum oils with sulfuric acid, sulfuric acid mono esters; phosphoric acid mono and d1 esters, including the corresponding thiophosphoric acids; phosphonic and arsonlc acids, etc.

Non-metallic detergents include compounds as the phosphatides (such as lecithin); certain fatty oils as rapeseed oils: voltolized fatty or mineral oils; etc.

Other detergents are the alkali earth phosphate di-esters, including the thiophosphate diesters; the alkali earth diphenolates, specifically the calcium and barium diphenol mono and poly sulfides.

Anti-oxidants whch may be present comprise several types, for example, alkyl phenols such as 2, 4, G-trimethyl phenol, pentamethyl phenol, 2, 4-dimethyl-G-tertiary-butyl phenol, 2, 4-dimethyl 6-octyl phenol, 2, 6-ditertiary-butyl-4-methyl phenol, 2, 4, G-trI-tertIary-butyl phenol, etc.; amino phenols as benzyl amino phenols; amines such as dibutyl phenylene diamlne, diphenyl amine, phenyl-alpha-naphthyl amine, phenylbeta-naphthyl amine, dinaphthyl amines: etc.

Antioxidant sulfur may be in the form of mercaptans, as in decyi mercaptains, dodecyl mercaptans, cetyl mercaptans, oleyl mercaptans, stearyl mercaptans, butyl or other higher allwl .thiophenes, thionaphthols, alkyl thionaphthols,

taining the sodium salt however, produced only a very small deposit of unusually soft carbon.

This sodium heptadecyl phthalate also proved to be an excellent peptizer and anti-ringsticking compound as determined by 40 hour lubricating oil tests in a standard Lauson engine operated at a jacket temperature of 100 C. r

The compounds of this invention may, if desired, be advantageously used in connection with other lubricating oil additives, for example, auxiliary detergents formed from the oil-soluble salts of various-bases with other detergent form.- ing acids. Such bases include metallic as well as organic bases. Metallic bases include those of the alkali metals, as well as Cu, Mg, Ca, Sr, Ba. Zn, Cd, Al, 8n, Pb, Cr, Mn, Fe, Ni, G0, etc. Organic bases include various nitrogen bases as prim rs. secondary. ter iary and quaternary amines.

Examples of detergent forming acids are the etc.; or of .disulfldes (RSSR', as in diamyl disulfide and higher dialkyl disuifldes, e. g. wax disulfides, diphenyl disulfides, dibenzyl disulfide, dlnaphthyl disulfldes, etc); or of sulfur compounds formed by attaching sulfur to an olefinic double bond --(as by reacting sulfur with olefins at temperatures of about 150 C. to 300 C.) which compounds are believed to contain the structure (sulfur in epithio linkage).

Many sulfur compounds naturally occurring in petroleum oils are useful antioxidants, provided they have the necessary reactivity. These have been described in detail in the copending application, Serial No. 496,678, flied July 28, 1943, by Paul R. Van Ess, Forrest J. Watson and Gary N. Whitney.

Thiazoles such. as mercaptobenzothiazole are I also good antioxidants.

Among the sulfurized oleflns found to be especially useful are, for example: sulfurized paraffln wax (as produced by chlorination of paraflln wax, having a molecular weight between about 225 and 425, dehydrochlorination of the chlorinated product to produce wax oleflns, and sulfurization of the latter) sulfurired olefin'or diolefin polymers boiling above about 400 C. such as are obtained as by-prcducts in the refining of cracked distillatcs with clay or other refining agents, or in the polymerization of normally gasseous olefins to produce gasoline or the like (e. g. sulfurlinoleate: sulfurlzed sperm oil, suliurized jojoba oil; etc.

Corrosion inhibitors may also be present such as dicarboxylic acids of 16 and more carbon atoms, alkali metal and alkali earth salts of suli'onic acids and fatty acids, organic compounds containing a nitrile, .nitro, or nitroso radical attached to a carbon atom which is alpha or beta to an acidic radical as in alpha cyano stearic acid, alpha hydroxy fatty acid esters, oxalic acid esters, organic amines, etc.

Likewise, other additives such as blooming agents, anti-foaming-agents, viscosityregulators, etc. may also be present in the lubricating oil.

The invention claimed is: a

1. A mineral lubricating oil suitable for internal combustion engines, containing dissolved a carbon softening amount of an oil-soluble alkali metal salt of a phthalic acid mono alkyl ester in which the alkyl radical contains about to 20 carbon atoms and has at least two atoms selected from the class consisting of tertiary and quaternary carbon atoms.

2. A mineral lubricating oil suitable for internal combustion engines, containing dissolved about 0.25% to 10% of an-oil-soluble alkali metal salt of .a phthalic acid mono alkyl ester in which the alkyl radical contains about 10 to 20 carbon atoms and has at least two atoms selected from the class consisting of tertiary and quaternary carbon atoms.

3. A mineral lubricating oil suitable for internal combustion engines, containing dissolved a carbon I softening amount of an oil-soluble sodium metal salt of a phthalic acid mono alkyl ester in which the alkyl radical contains about 10 to 20 carbon atoms and has at least two atoms selected from the class consisting of tertiary and quaternary carbon atoms.

4. A mineral lubricating oil suitable for internal combustion engines, containing dissolved a carbon softening amount of an oil-soluble potassium metal salt of a phthalic acid mono alkyl ester in which the alkyl radical contains about 14 to 20 carbon atoms and has at least two atoms selected from the class consisting of tertiary and quaternary carbon atoms.

5. A mineral lubricating oil suitable for internal combustion engines, containing dissolved a carbon softening amount of an oil-soluble lithium metal salt .01 a phthalic acid mono alkyl ester in which the allwl radical contains about 10 to 20 carbon atoms and has at least two atom selected from the class consisting of tertiary and quaternary carbon atoms.

6. A mineral lubricating oil containing dissolved a detergent amount of an oil-soluble compound oi the .formula COM V wherein R is a branched aliphatic radical havin 10-20 carbon atoms and imparting oil-solubility to the compound and has at least two atoms selected from the clas consisting of tertiary and quaternary carbon atoms and M is an alkali metal.

7. A mineral lubricating oil containing dissolved a detergent amount of an oil-soluble compound of the formula c COR 0 wherein M is an alkali metal and R is a branched aliphatic radical having no more than one olefinic double bond and containing about 14 to 20 carbon atoms which render the compound oil soluble and has at least two atoms selected from the class consisting of tertiary and quaternary carbon atoms.

8. A mineral lubricating oil containing dissolved a detergent amount of an oil soluble compound of the formula- I CaHs F-O-MCsHr-C wherein M is an alkali metal.

FULTON L. JOHNSTON. 

